In general, the processing of black-and-white silver halide photographic materials is performed in the order of development, stopping, fixing and washing.
Development is ordinarily carried out with aqueous alkaline developer compositions containing a developing agent, usually of the dihydroxybenzene type such as hydroquinone. The activity of these developing agents is greatly influenced by the pH of the solution and the optimum pH range should not significantly change during the useful life of the developer composition; therefore the composition possesses a high buffering capacity. The developer compositions are usually provided with antifogging agents (in particular inorganic antifogging agents such as soluble bromides and organic antifogging agents) to retard the development of non-exposed silver halide grains and decrease fog, i.e. silver formed as a result of the spurious development of said grains.
Antioxidant compounds are usually added to the alkaline developer composition to limit oxidation of the developing agents by air. Alkaline and ammonium sulfites are the most common compounds used for this purpose, but other antioxidant compounds such as hydroxylamine and ascorbic acid can be used instead of or in combination with such sulfites.
In graphic arts, there are two different conventional processing systems well known in the art. The "rapid access" and the "lith" processing system, able respectively to treat a "rapid access" film and a "lith" film. The "rapid access" processing system is characterised by the combination of a hydroquinone developer and an auxiliary developing agent, such as 3-pyrazolidone compounds or amino-phenol compounds, and high sulfite content. It has the advantage of wide processing latitude and excellent chemical stability, but the dot quality obtained is relatively poor. The "lith" processing system is characterised by a low free sulfite content and the application of hydroquinone as sole developing agent, as described by J. A. C. Yule in the Journal of the Franklin Institute, Vol. 239,221-230 (1945). It produces excellent dots and print results, but has very poor chemical stability and it needs long developing times.
Several alternatives to using a hydroquinone developing agent with a low sulfite content of the "lith" processing system to achieve high contrast development are known in the art. They are the so-called "high contrast" processing systems which use a hydrazine compound, either in the photographic element or in the developing solution, to promote high contrast, as described in U.S. Pat. No. 4,168,977. In U.S. Pat. No. 4,269,929, high contrast development of photographic elements is carried out in the presence of a hydrazine compound with an aqueous alkaline developing solution which has a pH of about 10 and below 12 (in the working examples the pH value is higher than 11) and contains a dihydroxybenzene developing agent, a 3-pyrazolidone developing agent, a sulfite preservative and a contrast-promoting amount of an amino compound. U.S. Pat. No. 4,172,728 describes a photographic developer containing hydroquinone, an auxiliary developer such as 1-phenyl-3-pyrazolidone, high sulfite content and an organic base such as diethanolamine; the developer is useful for processing lith film in rapid access machine processors to produce high contrast images. Additional patents on hydrazine compounds for high contrast images are U. S. Pat. Nos. 4,166,472; 4,221,857; 4,224,401; 4,237,214; 4,241,164; 4,272,606; 4,272,614; 4,311,781; 4,323,643; 4,332,878 and 4,337,634. However, relatively high pH levels in developing solutions containing hydrazide compounds, or in developing solutions used with photographic elements which contain hydrazine compounds, are needed in order to get the maximum improvement in contrast from the use of hydrazine compounds. The use of such high pH levels reduces the effective life of the developing solutions.
High contrast developing compositions which contain amino compounds and are intended for carrying out development in the presence of a hydrazine compound are also disclosed in U.S. Pat. Nos. 4,668,605 and 4,740,452. In fact, U.S. Pat. No. 4,668,605 describes developing compositions containing a dihydroxybenzene, a p-aminophenol, a sulfite, a contrast-promoting amount of an alkanolamine comprising a hydroxyalkyl group of 2 to 10 carbon atoms and a mercapto compound. The developing compositions of U.S. Pat. No. 4,740,452 contain a contrast-promoting amount of certain trialkyl amines, mono- alkyl-dialkanolamines or dialkylmonoalkanol amines. However, the need to use the contrast-promoting agent in a large amount and the volatility and odor-generating characteristics of amino compounds that are effective in enhancing contrast represent disadvantageous characteristics of the developer solutions therein described.
Recently, it has been found that well defined photographic elements can be developed in developing solutions having pH below 11.0. For example, U.S. Pat. No. 4,975,354 discloses photographic elements, particularly useful in the field of graphic arts, which are capable of high contrast development, when processed in the presence of a hydrazine compound that functions as a nucleating agent. The elements include certain amino compounds which function as incorporated boosters. The characteristics of the compounds contained in the photographic element allow the photographic element to be processed in a developer solution having a pH value in the range of 9 to 10.8.
European Patent application No. 446,078 describes a silver halide photographic material containing a novel compound for photomechanical processes as a contrast promoting agent. In the example, two developer solution compositions have been mixed to obtain a working solution having a pH value below 11. The first developer solution composition comprises a high molar ratio of buffering agent versus developing agent; the second developer solution composition comprises a 1-phenyl-3-pyrazolidone compound as auxiliary developing agent and a contrast promoting agent. Good dot quality and low pepper fog are claimed.
At present, in order to develop "rapid access" and "high contrast" films, two different types of chemical developing solutions must be used, with the disadvantage that the operator must change the developer solution each time he has to develop a film of the type different from the last one developed by the same developing apparatus. The only alternative is to use two different developing apparatus, the first one containing a "high contrast" processing system, and the second one containing a "rapid access" developing system.
It is desirable to have a stable developing solution, having a pH value below 11.0, able to develop both a "high contrast" film and a "rapid access" film, giving at the same time high contrasts by development of silver halide photographic elements.